Overview

Many materials are subjected to forces or loads when in use. In such situations, it is necessary to know the characteristics of the material and to design the member in order to avoid failure during the expected life and service environment of the material. Key mechanical design properties are stiffness, strength, hardness, ductility, and toughness. Factors to be considered include the nature of the applied load and its duration, as well as the environmental conditions. The applied loads could be tensile, compressive, or shear and their magnitudes may be constant with time or may fluctuate continuously. Application time may be only a fraction of a second, or it may extend over a period of many years. Service temperature may be an important factor. In this lesson, we will introduce how the various mechanical properties are measured and what these properties represent.

Learning Objectives

By the end of this lesson, you should be able to:

• Define stress and strain.
• Define elastic region, plastic region, fracture point, elasticity, tensile strength, and the yield strength.
• Given a stress-strain diagram, determine elastic region, plastic region, fracture point, elasticity, tensile strength, and the yield strength.
• Distinguish between tensile, compressive, shear, and torsional stress.
• Define hardness, resilience, and toughness.
• Evaluate whether a material is ductile or brittle using a stress-strain diagram.

Lesson Roadmap

Lesson 4 will take us 1 week to complete. Please refer to Canvas for specific due dates.

Questions?

If you have general questions about the course content or structure, please post them to the General Questions and Discussion forum in Canvas. If your question is of a more personal nature, feel free to send a message to the instructor through Canvas email. The instructor will check daily to respond.